The present invention relates generally to an apparatus and method for packaging food items and more particularly to an apparatus and process for packaging and stacking food items in hermetically sealed individual slices.
Various methods and apparatus have been proposed and utilized for the manufacture and packaging of individual slices of food items such as cheese. Although the available apparatus and methods are suitable for the packaging of individual slices, they are not without disadvantages.
Typically, the package for the individual slices is formed from a continuous film or web of a thermoplastic material. The web is first folded in V-folded condition. As used herein, the term V-folded condition refers to a length of material which has been folded over onto itself so as to form what may subsequently be identified as a front sheet and a rear sheet which are joined by the fold at the bottom, so as to approximate the letter "V" in cross section. The web is typically folded such that the rear sheet is longer than the front sheet to define a flap section in the rear sheet, which extends beyond the top edge of the front sheet. The flap section is typically folded over onto the front sheet to form a tubular web.
After the flap is folded over on the front sheet, a tubular web is defined The processed cheese is then inserted into the tube and the web and cheese are flattened. Subsequently cross-seals are formed along the longitudinal length of the tubular web at predetermined intervals. After the tube is cross-sealed it is severed along the cross-seals in order to produce the individually wrapped slices of cheese Several processes presently exist for providing the transverse or cross seal.
In one commonly used method, the cross-seals are formed by subjecting the flattened web (with the inserted cheese) to pressure, at the desired location, to form the transverse cross seal. The pressure is applied such that an ultra thin layer or film of cheese is left in the transverse sealing section. The ultra thin layer or film of cheese acts as an adhesive to seal the two layers of the plastic web together. After this "cheese" seal has been formed, the web is severed at the sealed sections to define individual slices of cheese.
Although the "cheese" seal provides an adequate seal for the individual slices of cheese, the shelf life of the cheese product after it is packaged is not as long as would be desirable. This is due to the fact that the cheese seal is a relatively weak seal which will eventually deteriorate and which allows air to enter into the slices under ordinary atmospheric conditions. The slices will soon dry out or spoil.
Other methods of providing a transverse cross-seal have also been disclosed. For example, U.S. Pat No. 4,586,317 (Bussell) discloses an arrangement for forming a seal in packaging material (such as processed cheese) which utilizes a sealing element having a finite number of small channels in the surface. The packaging film is co-extruded or laminated to include an inner sealing layer of relatively low thermal plastic melt temperature and an outer layer which does not melt under sealing conditions. The tube is heated and compressed transversely by the sealing elements thereby sealing the internal layers of the packaging film together. Although the apparatus and method disclosed in this patent provide a suitable cross-seal, the finished product suffers from the same disadvantages that are described above. Since the longitudinal seal is formed by providing a flap in the V-folded condition web and simply overlapping the flap with the upper surface of the front sheet of the web, a poor seal is formed Thus, air and other atmospheric products will enter into the wrapped slices of cheese, reducing the shelf life of the product
Therefore it would be desirable to provide an individual slice of cheese which is wrapped in a package which is hermetically sealed on all sides. To accomplish this, a hermetic seal must be formed along the longitudinal edge of the web as well as along the transverse or cross-seals. A hermetically sealed package would have several advantages. For example, a hermetically sealed slice would permit immersion for cooling and sanitizing. Further, a hermetically sealed slice is essential to aseptic packaging.
For purposes of manufacturing economy, it would be desirable to provide the longitudinal seal and cross-seals in a continuous process. Some presently available methods, however, form seals in an intermittent fashion. Typically, in these presently available methods, a seal is formed by heated jaws which reciprocate between an open and a closed position. When the jaws close, they seal the desired section of the web. After the section has been sealed, the jaws retract and the web is moved for the next section which is to be sealed. This process, however, has obvious disadvantages. The web must be continuously stopped and started in accordance with the reciprocating movement of the jaws. Such a device is disclosed for example in U.S. Pat. No. 2,460,460 (Langer).
Another problem which is encountered in the processing and packaging of cheese slices (as well as in the packaging of other products which are packaged in slices) is the lack of an available simple and efficient stacking process Typically the stacking of slices into packages containing a plurality of slices is performed by an operator or a stacking machine The available stacking machines, however, do not provide the required degree of efficiency and precision in the packaging of different stacks of cheese It would be desirable to provide a stacking arrangement or process which would permit slices from a single wrapping machine to be stacked in a plurality of different stacks. It would be even more desirable to provide an arrangement which would allow the operator to selectively vary the number of slices in the stacks from one stacking job to the next. Preferably the stacking arrangement will also accurately stack slices of cheese from a relatively fast production line in a plurality of different stacks.
Therefore, in view of the above, it is an object of the present invention to provide an apparatus and a method for producing individual slices of food items, such as processed cheese, which are hermetically packaged.
It is a further object of the present invention to provide an apparatus and method for providing a continuous and efficient arrangement for forming hermetic seals along all of the edges of the packaging web.
It is still a further object of the present invention to provide an apparatus and method for stacking the desired number of the slices of food items, such as cheese, in the stacking locations from a rapid packaging system.